Effects of aflatoxin ingestion on the development of Moraxella bovis infectious bovine keratoconjunctivitis

A study was conducted to determine whether measured doses of aflatoxin given under different schedules would influence the pathogenesis of Moraxella bovis induced infectious bovine keratoconjunctivitis (IBK). Calves were allotted to 4 groups (groups I-IV) of 9, 9, 9, and 8 calves, respectively. Group I calves were given aflatoxin for 11 consecutive days starting 5 days before their eyes were exposed to M. bovis. Group II calves were given aflatoxin for 5 consecutive days starting 7 days after their eyes were exposed to M. bovis. Group III calves were given aflatoxin for 5 consecutive days starting 21 days after their eyes were exposed to M. bovis. Group IV calves were not given aflatoxin; but their eyes were exposed to M. bovis on the same day as were the eyes of calves in groups I-III; these calves served as controls. Aflatoxin had little if any influence on the pathogenesis of IBK under the conditions of this study. The results did not rule out an exacerbating effect of M bovis infection on aflatoxicosis in calves. Calves with the highest concentration of aflatoxin in their blood had the more severe signs of aflatoxicosis. Possible reasons for the equivocal results are discussed.     

Biological suppression of aflatoxicosis in Japanese quail (Coturnix coturnix japonica) by dietary addition of yeast (Saccharomyces cerevisiae).

The amelioration of aflatoxicosis in Japanese quails was examined by the dietary addition of live yeast (Saccharomyces cerevisiae; SCE). Yeast incorporated into the diet at 1 g kg(-1) was evaluated for its ability to reduce the deleterious effects of 2.5 mg total aflatoxin (AF; 82.30 per cent AFB1, 2.06 per cent AFB2, 7.68 per cent AFG1 and 7.96 per cent AFG2) kg(-1)diet on growing Japanese quail chicks from 10 days to 45 days of age. Forty 10-day-old Japanese quail chicks were assigned to 2x2 factorial arrangement of treatments (control, AF, SCE, AF plus SCE) each consisting of 10 quails. The performances of birds were evaluated. The AF treatment significantly and dramatically decreased food consumption and body-weight gain from the first week onwards. The significant adverse effect of AF on the food conversion ratio was also determined from week 1 to the end of the experiments. The addition of SCE to the AF -containing diet significantly reduced these deleterious effects of AF on food consumption, body-weight gain and food conversion ratio. Compared to controls, the cumulative body weight gain was reduced by 37 per cent among the quails consuming AF without SCE, but increased 15 per cent for the birds fed AF plus SCE. Interestingly, the single inclusion of SCE to the AF-free diet provided significant improvements in all the investigated growth performances of birds (approximately 40 per cent) compared to controls.     

Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens.

Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.     

Dietary L-carnitine increases plasma insulin-like growth factor-I concentration in chicks fed a diet with adequate dietary protein level

1. The effect of L-carnitine supplemented into experimental diets with varying dietary protein concentrations (50, 200 and 400 g/kg) on body weight gain and plasma insulin-like growth factor-I (IGF-I) concentration in chicks was examined. 2. Dietary L-carnitine supplementation provided 0, 200, 500 and 1000 mg/kg. Chicks were given the diet ad libitum for 10 d. 3. When L-carnitine was provided as 500 or 1000 mg/kg, body weight gain was significantly improved in birds receiving the 200 and 400 g protein/kg diets. 4. There was an interaction between dietary L-carnitine and protein content on plasma IGF-I concentration. L-carnitine supplementation had little influence on plasma IGF-I concentrations in birds receiving the low protein (50 g/kg) diet. When dietary L-carnitine concentrations were increased from 0 to 1000 mg/kg in the adequate protein (200 g/kg) diet, plasma IGF-I concentrations were also increased. However, when dietary L-carnitine content was more than 500 mg/kg in the 400 g/kg protein group, plasma IGF-I concentration decreased with increasing dietary L-carnitine content. 5. Body weight change correlated significantly with the alteration in plasma IGF-I concentrations in chicks given diets with adequate dietary protein. 6. In conclusion, the improvement in body weight gain caused by dietary L-carnitine supplementation was achieved when chicks were given their dietary protein requirement, which may be partially explained by an increase in plasma IGF-I concentration.     

Biological suppression of aflatoxicosis in Japanese quail (Coturnix coturnix japonica) by dietary addition of yeast (Saccharomyces cerevisiae)

The amelioration of aflatoxicosis in Japanese quails was examined by the dietary addition of live yeast (Saccharomyces cerevisiae; SCE). Yeast incorporated into the diet at 1 g kg⁻¹was evaluated for its ability to reduce the deleterious effects of 2·5 mg total aflatoxin ( ; 82·30 per cent ₁ , 2·06 per cent ₂, 7·68 per cent ₁and 7·96 per cent ₂) kg⁻¹diet on growing Japanese quail chicks from 10 days to 45 days of age. Forty 10-day-old Japanese quail chicks were assigned to 2×2 factorial arrangement of treatments (control, , , plus ) each consisting of 10 quails. The performances of birds were evaluated. The treatment significantly and dramatically decreased food consumption and body-weight gain from the first week onwards. The significant adverse effect of on the food conversion ratio was also determined from week 1 to the end of the experiments. The addition of to the -containing diet significantly reduced these deleterious effects of on food consumption, body-weight gain and food conversion ratio. Compared to controls, the cumulative body weight gain was reduced by 37 per cent among the quails consuming without , but increased 15 per cent for the birds fed plus . Interestingly, the single inclusion of to the -free diet provided significant improvements in all the investigated growth performances of birds (approximately 40 per cent) compared to controls.     

Dietary L-carnitine supplementation enhances the lipopolysaccharide-induced acute phase protein response in broiler chickens

The objective of the present study was to evaluate the potential effects of dietary L-carnitine supplementation on acute phase protein response upon a lipopolysaccharide (LPS) challenge of male broiler chickens receiving a commercial broiler diet supplemented with 15 or 100 mg L-carnitine/kg or an unsupplemented (control) diet from 14 days of age onwards. At 28 days of age, eight chickens per dietary treatment were weighed and subcutaneously injected with 300 microg LPS from E. coli (100 microg LPS/ml saline) or 3 ml saline (unsupplemented group only). During the next 10 days, blood samples were taken repeatedly and analysed for their hemopexin (HX) and alpha-1 acid glycoprotein (AGP) levels. Extra dietary L-carnitine did not affect broiler performance. At day 1 postinjection, plasma HX and AGP levels were significantly increased in all treatment groups. However, the elevations in circulating HX and AGP levels were more pronounced in the L-carnitine supplemented chickens, especially in the 100mg L-carnitine group. It is concluded that extra L-carnitine in the diet of broiler chickens enhances or advances the acute phase protein response. The exact mode of action needs to be elucidated but seems to be consistent with a glucocorticoid mimicking effect.     

Effect of oral L-carnitine on its concentration in the plasma of yearling Thoroughbred horses

After an oral dose of 10 g of L-carnitine the plasma concentrations of free and total carnitine increased in five yearling thoroughbred horses, reaching a peak two to four hours after administration, but in two horses there was no increase. In the five which responded, the mean (+/- sd) peak increase in total carnitine concentration was 15.1 +/- 6.9 mumol/litre from a predose mean of 18.8 +/- 3.4 mumol/litre, and the mean peak increase in free carnitine concentration was 13.5 +/- 3.1 mumol/litre from a pre-dose mean concentration of 12.5 +/- 2.2 mumol/litre. These changes were similar to those observed previously in a group of adult thoroughbred horses given 10 g of L-carnitine. There was no consistent pattern of change in the concentration of acetylcarnitine in the seven yearling horses.     

Effectiveness of melatonin on aflatoxicosis in chicks

The efficacy of melatonin co-administration on aflatoxicosis in chicks was investigated. Ross PM3 breed chicks were divided into groups of 10 and given conventional feed. One of the groups was kept as a control (C), and the others were given 150 ppb aflatoxin (AF1), 300 ppb aflatoxin (AF2), 150 ppb aflatoxin plus 10 mg/kg/bwt melatonin (AF1+M), 300 ppb aflatoxin plus 10 mg/kg/bwt melatonin (AF2+M), 10 mg/kg/bwt melatonin (M), and 1% ethanol (E). After 21 day-treatment period, the chicks were sacrificed, liver and kidney tissues were collected, processed for immuno-histochemical staining, in situ TUNEL method, and biochemical analyses. Vacuolar degeneration, necrosis, bile duct hyperplasia in liver, and mild tubular degeneration in kidney were detected in AF groups. Pathological changes were markedly reduced in AF+M groups, and a microscopic view similar to group C was observed. Increased immunoreactivity against inducible nitric oxide synthase (iNOS) and nitrotyrosine was detected in AF groups compared to weak immunoreactivity in group C. Immunoreactivity in AF+M groups was markedly reduced compared to AF groups and was similar to group C in liver and kidney. Many apoptotic cells were detected in the livers of AF groups, whereas there were no apoptotic cells in AF+M groups. While reduced glutathione (GSH) levels in liver and kidney of AF groups were greatly reduced, malondialdehyde (MDA) levels increased. With melatonin co-administration, the levels of GSH and MDA approached to the values of group C. These results indicated that nitrosative tissue degeneration caused by aflatoxin could be greatly reduced by melatonin supplementation in chicks.     

The effect of supplementation of clove and agrimony or clove and lemon balm on growth performance, antioxidant status and selected indices of lipid profile of broiler chickens

The study investigated the effects of diet supplementation with 1% clove flower buds powder combined with either 0.2% lemon balm extract or 0.2% agrimony extract (each of the two pulverized extracts supplied through drinking water) on body weight of broilers, total feed intake, feed conversion ratio and the carcass yield, activity of superoxide dismutase (SOD, EC 1.15.1.1) and glutathione peroxidase (GSH‐Px, EC 1.11.1.9) in blood, concentration of sulfhydryl (?SH) groups, malondialdehyde (MDA), vitamin A and E, low‐density lipoproteins in the blood plasma, serum cholesterol, total lipids, triglycerides and high‐density lipoproteins in broiler chickens at 42 days of age. On the day of hatching, 120 male and female broilers of Cobb 500 were randomly divided into three groups. The control group (1st group) of broilers received a basal diet (BD) without any feed and water additive. Both experimental groups of chicks were fed BD enriched with clove (Syzygium aromaticum L.) powder at a dose of 10 g/kg DM for 42 days. Moreover, either lemon balm (Mellisa officinalis L.) extract or agrimony (Agrimonia eupatoria L.) extract diluted with drinking water (2:1000) was given to broilers in the 2nd and 3rd group respectively. The results indicated that feeding the diets enriched with selected herbal supplements failed to affect the growth performance of broiler chickens at 42 days of age. In addition, this supplementation had no influence on the activities of SOD and GSH‐Px, concentration of vitamin A and selected lipid metabolism indices. On the other hand, we observed beneficial effects on some indices of the antioxidant status (increased concentration of ?SH groups and vitamin E, decreased concentration of MDA) in the blood of broilers in both experimental groups in comparison with the control group of chickens (p < 0.05). Furthermore, a slightly better antioxidant capacity was found in the blood of broilers supplied the combination of clove and lemon balm compared to clove and agrimony (vitamin E, 11.26 ± 0.73 vs. 9.73 ± 0.64 μmol/L, p < 0.05 respectively). It could be concluded that supplementation of the diet with clove flower buds powder combined with lemon balm extract or agrimony extract dissolved in drinking water has a potential to increase the antioxidant status but fails to influence either the growth performance or the selected lipid metabolism indices of broilers at the age of 42 days.     

Physiological performance of quails that underwent dietary and pharmacological manipulation of cholesterol

The present work evaluated whether dietary and pharmacological interference on cholesterol synthesis were capable of inducing alterations in blood and yolk cholesterol levels and the secretion of corticosterone metabolites. Forty‐five 40‐day‐old quails were divided into three experimental groups: vegetal fat diet, 2% beef fat (tallow) diet and vegetal fat diet with simvastatin administration (3.13 mg/kg/day). During all experiments, the animal weights and food consumption were recorded and blood and faecal samples (days 0, 15, 30, 45 and 60), as well as eggs (days 30, 45 and 60), were collected. Analysis of serum and yolk cholesterol was performed and faecal corticosterone levels were measured. No differences were observed on blood cholesterol or faecal corticosterone between all treatments, despite a tendency of increased cholesterol in the group with the animal fat diet. However, quails submitted to an animal fat diet displayed an increase in yolk cholesterol at day 30 of the treatment and the egg yolks of quails treated with simvastatin exhibited a decrease in cholesterol content by the end of the treatment at 60 days. These results improved the knowledge regarding the physiology of quails and offered support to other studies concerning the consequences of the pharmacological treatment and the dietary manipulation of cholesterol levels.     

Disseminated intravascular coagulation in dogs with aflatoxicosis

During an outbreak of aflatoxicosis in dogs living in Sao Paulo, two cases of disseminated intravascular coagulation were observed in association with the ingestion of an aflatoxin contaminated dog food. The first dog, a four-year-old, male, German shepherd developed haematemesis, melaena, petechial haemorrhages and jaundice progressing to uraemia, encephalopathy and death. The second dog, an 11-month-old, female, basset hound showed jaundice and ascites with no obvious haemor-rhagic signs, except the persistence of bleeding at the sites of venepunctures and petechiae on the oral mucosa. As overall signs deteriorated and evolved to uraemia, the dog was killed. Both had a prolonged whole blood clotting time (120 and 12 minutes), one stage prothrombin time (300 and 24 seconds) and activated partial thromboplastin time (320 and 180 seconds), reduction in the plasma fibrinogen (0–14 g/litre and 0–6 g/litre), thrombocytopenia (150 × 10⁹/litre and 32 × 10⁹/litre) and a positive protamine sulphate test, indicating the presence of fibrin monomers. The occurrence of disseminated intravascular coagulation was confirmed by the observation of multiple areas of infection in kidney and lung and by the presence of fibrin clots inside pulmonary vessels.     

In vivo antioxidant properties of vitamin E and chromium in cold-stressed Japanese quails.

An experiment was conducted to determine if vitamin E (alpha-tocopherol-acetate) and chromium (chromium picolinate, Cr Pic) supplementation attenuate the negative effects of cold stress on egg production, egg quality, serum metabolites, and antioxidant status in Japanese quails (Corurnix coturnix japonica). One hundred and fifty laying Japanese quails (50-day-old) were divided into five groups, 30 birds per group. The laying quails kept at 6 degrees C for 12 h/d (08.00 p.m. to 08.00 a.m.) were fed either a basal diet (low temperature-basal diet, CS group) or the basal diet supplemented with either 400 microg of Cr/kg of diet (Cr group), 250 mg of alpha-tocopherol-acetate per kg of diet (Vit. E group) or 400 microg of Cr plus 250 mg of alpha-tocopherol-acetate per kg of diet (Vit. E + Cr group) while quails kept at 18 degrees C were fed a basal diet (thermo-neutral-basal diet, TN group). Performance and egg quality were significantly reduced in CS group compared with TN group. Supplemental chromium and vitamin E significantly increased live weight change, egg production, and improved feed efficiency in cold-stressed laying hens compared with the group fed the basal diet at 6 degrees C. Egg production and egg weight were also greater (P < 0.05) in each supplemental group compared with the CS group. However, a combination of vitamin E and chromium, rather than each separately, provided the greatest performance. Supplemental vitamin E and chromium also increased serum vitamin C and E but, decreased malondialdehyde (MDA) concentrations (P < 0.05); the combination of vitamin E and chromium resulted in the highest levels of serum vitamin C and E within the cold-stressed quails. Results of the present study indicate that combined antioxidant supplements increased performance, egg quality and serum antioxidant levels while lowering MDA in cold-stressed quails.     

Effects of L-carnitine administration on growth performance, carcass traits, blood serum parameters and abdominal fatty acid composition of ducks.

Effects of L-carnitine administration via drinking water on growth performance, carcass traits, blood serum parameters and abdominal fatty acid composition of ducks was examined. One hundred day-old Turkish native duck chicks were divided into two groups, each with five replicates and given the same diets with 0 and 200 mg/l carnitine chlorhydrate via drinking water. The study lasted 8 weeks, with the first 4 weeks as a starter and the last 4 weeks as grower period. At the end of the study five ducks were randomly selected from each subgroup for slaughter. Growth performance parameters of ducks were not affected significantly by L-carnitine administration. Live weight, daily weight gain, cumulative feed consumption and average feed conversion efficiency were found to be 1490 and 1621 g, 26.0 and 28.1 g, 5386 and 5662 g, 3.75 and 3.54 kg/kg in the control and in the carnitine groups respectively. L-carnitine administration did not effect carcass traits and serum cholesterol, total lipid, triglyceride and glucose levels. Total saturated fatty acid content of abdominal fat significantly decreased, mono- and polyunsaturated fatty acid content were not affected by L-carnitine administration. In conclusion, L-carnitine administration by drinking water did not affect growth performance, carcass traits and blood parameters in ducks.     

Effects of oral L-carnitine, L-lysine administration and exercise on body composition and histological and biochemical parameters in pigeons

The purpose of this study was to examine whether L-carnitine and its precursor L-lysine could have any beneficial effect in racing pigeons, and if so, whether this effect is influenced by the extent of exercise (short-distance flight: 135 km vs. long-distance flight: 580 km). Birds were divided into seven groups of animals. Group 1: negative control, no flight, no treatment, Group 2: positive control, placebo treatment before the short-distance flight, Group 3: 200 mg/day L-carnitine treatment before the short-distance flight, Group 4: 400 mg/day L-lysine treatment before the short-distance flight, Group 5: positive control, placebo treatment before the long-distance flight, Group 6: 200 mg/day L-carnitine treatment before the long-distance flight, Group 7: 400 mg/day L-lysine treatment before the long-distance flight. L-carnitine, L-lysine and distilled water (placebo) were orally administered (tube feeding) for 7 days before flight. Just after returning home, blood samples were collected and analyzed for glucose, fructosamine, cholesterol, triglycerides and thiobarbituric acid reactive substances. Pigeons were euthanized using carbon dioxide as an inhalation agent, and the whole body was subjected to proximate analysis. The status at arrival was referred to as a basis for comparison. Sex did not affect the measured parameters. As a result of the L-carnitine and L-lysine administrations, the body fat mobilization was higher during the 580 km flight, whereas no changes were noted during the 135 km flight. The main changes in the measured blood parameters were caused by the extent of exercise. This experiment considered the extent of exercise as a factor potentially modulating L-carnitine supplementation effects. In conclusion, flight distance affected several parameters but the supplements of L-carnitine and L-lysine were not effective in the tested situations.     

小麦日粮添加木聚糖酶对鹌鹑生长性能及免疫性能的影响

试验选取1日龄朝鲜龙城鹌鹑108只,研究小麦-豆粕型基础日粮添加木聚糖酶对鹌鹑生长性能及免疫性能的影响。试验鹌鹑按体重随机分为3个处理组,每个处理设3个重复,每重复12只。第1组设为对照,饲喂玉米-豆粕型基础日粮;第2组饲喂小麦-豆粕型基础日粮;第3组在小麦-豆粕型日粮中添加2000U/kg的木聚糖酶,试验期42d。结果表明:小麦日粮对育雏期(0~21日龄)鹌鹑生长性能无显著影响(P>0.05),但是显著降低育成期(22~42日龄)鹌鹑的体重和日增重(P<0.05)。小麦日粮中添加木聚糖酶2000U/kg,对鹌鹑的生长性能无显著影响(P>0.05)。小麦日粮组的新城疫抗体效价显著低于玉米对照组(P<0.05),但是小麦日粮可以显著提高细胞免疫水平(P<0.05)。添加木聚糖酶对鹌鹑的免疫性能无显著影响(P>0.05)。     

Effect of dietary antioxidant supplementation on the oxidative status of plasma in broilers

In this study, the effect of dietary antioxidants on the plasma oxidative status of growing birds fed a diet rich in polyunsaturated fatty acids was investigated. One‐day‐old broilers were fed for 42 days a diet containing 4% linseed oil and supplemented with single plant extracts rich in antioxidants (natural tocopherols, rosemary, grape seed, green tea, tomato) or a combination of some of these plant extracts, in two different total doses (100 and 200 mg product/kg feed). A diet with synthetic antioxidants with and without α‐tocopheryl acetate (200 mg/kg feed) were also included. The plasma oxidative status was evaluated measuring the ferric reducing ability of plasma (FRAP), the superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px) activity. Lipid peroxidation was measured by thiobarbituric acid‐reactive substances (TBARS). No significant effect of the dietary treatments was observed for FRAP as well as for TBARS. However, diet affected GSH‐Px activity (p = 0.002) and a trend for an effect on SOD activity was observed (p = 0.084). A higher GSH‐Px activity was found for 200 mg/kg tomato extract and natural α‐tocopherol in relation to the corresponding 100 mg/kg treatment, and the lowest GSH‐Px activity was measured for the synthetic antioxidants treatment. The lowest and highest SOD activity were found for the 200. and 100 mg/kg treatment with tomato extract respectively. In conclusion, the oxidative status and lipid oxidation of plasma in broilers was not affected by feeding natural antioxidant extracts at the doses in the present study, but some changes in antioxidant enzyme activities were observed, of which the implication remains to be elucidated.     

The effect of high doses of aflatoxin on the pig]

In two experiments, 18 pigs were given feed contaminated with aflatoxin which had been prepared by the extraction of the cultures of toxinogenic strains of the fungus Aspergillus flavus. After the ingestion of aflatoxin (AFB1) at a dose of 5.4 to 10.5 mg per kg of live weight, the pigs showed symptoms of peracute aflatoxicosis and died within 12--20 hours. After ingestion of AFB1 at a dose of 1.4 or 3.1 mg per kg live weight, the pigs suffered from acute aflatoxicosis and died within 3 to 26 days from the administration of the contaminated feed. In the cases of these experimental aflatoxicoses, clinical symptoms, haematological and biochemical changes in the blood and the patho-anatomical and histological findings in the swine organism were described.     

Use of L-carnitine and humate in laying quail diets

This experiment was carried out to determine the effects of using L-carnitine and humate alone or in combination in quail diets on laying performance, egg traits and blood parameters. A total of 280 Japanese quails aged 10 weeks, divided into one control group and three treatment groups, were used. The diets of the first, second and third treatment groups were supplemented with 100 mg L-carnitine/kg, 1.5 g humate (Farmagülat?r Dry Plus)/kg and 100 mg L-camitine + 1.5 g humate/kg, respectively. The experimental period lasted 16 weeks. The addition of L-carnitine and sodium humate alone or in combination did not significantly affect body weight, feed consumption, egg production, feed conversion ratio, mortality, egg-shell thickness, egg yolk index and the percentages of egg-shell, albumen and yolk. Egg weight increased (P < 0.001) with L-carnitine supplementation. The values of egg albumen height (P < 0.05), egg albumen index (P < 0.01) and egg Haugh unit (P < 0.05) were increased with humate supplementation. Egg cholesterol content and blood serum parameters were not affected by the supplementation of L-carnitine with or without humate. The results in this study demonstrated that L-carnitine supplementation increased egg weight while humate addition increased egg albumen index and egg Haugh unit of laying quails. However, the combined administration of L-carnitine and humate did not have any significant effects on the parameters measured.     

Transfer of chlortetracycline from contaminated feedingstuff to cows' milk

Three groups of four Friesian cows in mid-lactation were fed a compound feedingstuff contaminated with 2, 10 or 300 mg chlortetracycline/kg for 21 days, and were then fed an uncontaminated diet for seven days. A fourth group of four cows was fed an uncontaminated diet throughout the study. Daily pooled milk samples from each cow were analysed by high performance liquid chromatography (HPLC) with a detection limit of 50 microg chlortetracycline/litre. Chlortetracycline was detected in only two milk samples taken from one of the animals fed feed containing 300 mg 300 mg chlortetracycline/kg, and both contained less than the maximum residue limit (MRL) specified by the European Union (100 microg/litre). All the milk samples were also analysed by the Delvotest SP microbiological assay, which has a detection limit of 300 microg chlortetracycline/litre. During the treatment period, this method gave four presumptive false-positive results, because they were not confirmed by HPLC. Selected daily pooled samples from each treatment group were also analysed by the semi-quantitative Charm II radioreceptor assay with a detection limit of 10 microg chlortetracycline/litre. Immunoreactive chlortetracycline was detected only in the animals fed feed containing 300 mg chlortetracycline/kg and several of the results exceeded the EU MRL during the treatment period. No significant treatment effects on animal performance were observed. However, there was a trend towards a higher milk fat concentration (P<0.09) and a lower milk protein concentration (P<0.07) with increasing concentration of chlortetracycline in the diet.     

Ivermectin (3.15%) long-acting formulations in cattle: absorption pattern and pharmacokinetic considerations

Ivermectin (IVM) is a broad-spectrum antiparasitic drug extensively used in veterinary medicine. The composition of the pharmaceutical preparation affects IVM absorption and its systemic availability. After the introduction of the first approved IVM formulation (propylene glycol/glycerol formal 60:40) used at 200 microg/kg, different pharmaceutical modifications have been assayed to extend IVM persistent endectocide activity. Recently, IVM 3.15% long-acting (IVM-LA) preparations to be administered at 630 microg/kg to cattle were introduced into the veterinary pharmaceutical market. The work reported here was designed to evaluate the comparative IVM absorption pattern and plasma concentration profiles obtained after subcutaneous administration of the classic pioneer IVM formulation (1%) and two different commercially available IVM-LA preparations (3.15%) to cattle. Twenty-eight Holstein heifers were divided in four experimental groups (n=7) and treated subcutaneously as follows--Group A: IVM 1% given at 200 microg/kg, Group B: IVM 1% administered at 630 microg/kg, Group C: IVM-LA (A) injected at 630 microg/kg and Group D: IVM-LA (B) given at 630 microg/kg. Blood samples were taken between 0.5 and 90 days post-treatment and IVM plasma concentrations were determined by HPLC with fluorescence detection. There were no differences in the persistence of IVM plasma concentrations after the administration of IVM 1% formulation at the two used dose levels (200 and 630 microg/kg). Higher peak plasma concentration (C(max)) and shorter mean residence time (MRT) were obtained for IVM 1% given at 630 microg/kg (Group B) compared to the treatments with both IVM-LA preparations. The IVM-LA (A) formulation showed a more extended absorption process than IVM-LA (B) preparation, which accounted for a longer persistence of detectable IVM plasma concentrations. The parasitological implications of the observed differences in peak plasma concentrations (C(max) values) and in the IVM concentration levels measured from day 20, and afterwards until day 90 post-treatment, between the different preparations assayed need to be elucidated. The characterization of the absorption patterns and kinetic behaviour obtained after injection of these novel long-acting formulations used at three times the therapeutic dose recommended for the classic IVM preparation in cattle is a further contribution to the field.